Current digital displays employ an optically transmissive surface with a backlight that passes white light through a series of electronically controlled red, green, blue (RGB) optical filters. Image brightness is controlled by the backlight brightness setting and the RGB filter settings. Backlight brightness in turn is controlled by the electrical power applied by the associated backlight power module, as well as by the transmission efficiency of the actual backlight device.
Portable applications such as notebook computers often prefer to minimize the power drain from their local battery source. Digital displays often consume 25-50% of the total average system application power consumption, with the backlight representing a major percentage of the total display power.
Common digital displays often employ a cold-cathode fluorescent lamp (CCFL) as the primary backlight source. CCFL light output is a function of the input power applied to it, as well as the lamp operating temperature. Higher light output levels often result in a form of self-heating that helps reduce the amount of electrical power necessary per unit of luminance. Conversely, applications which run at the lower range of available lamp luminance may require a larger amount of electrical input power to achieve a given level of luminance.